[Samba] Problem with AIO random read

[Volker Lendecke]

On Wed, Dec 03, 2014 at 03:45:24AM -0800, mikeliu wrote:
> Hello list,
> 
> I setup Iometer to test AIO for 100% random read.
> If "Transfer Request Size" is more than or equal to 256 kilobytes,in the
> beginning the transmission is good.
> But 3~5 seconds later,the throughput will drop to zero.
> 
> Server OS:
> Ubuntu Server 14.04.1 LTS
> 
> Samba:
> Version 4.1.6-Ubuntu
> 
> Dialect:
> SMB 2.0
> 
> AIO settings :
> aio read size = 1
> aio write size = 1
> vfs objects = aio_pthread

Please don't use this module. pthread aio is built in for
4.1. aio_pthread is only used for creating files
asynchronously, read/write is done without any special
module.

Removing that module won't help you probably though. We need
to really take a look at what's happening, this should just
work fine.

When the system is stalled, how many threads does the smbd
have active? /proc/pid/tasks will tell you. Also, can you
attach to smbd with gdb and show a backtrace?

Maybe it does not happen anymore under strace, but could you
strace -f that smbd while its running into the issue?

Ah, btw, you don't happen to have sendfile/recvfile active?
I think those don't play well with aio.

With best regards,

Volker Lendecke

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